Introduce from statement

[white-gecko]

We could add a from statement to the beginning of a dld.yml file which includes another dld.yml file to e.g. reuse some basic setup.

This would e.g. look like this:

basic/dld.yml

components:
    store:
        image: aksw/dld-store-virtuoso7
        ports: ["8895:8890"]
    load:
        image: aksw/dld-load-virtuoso

ontowiki/dld.yml

from "../basic/dld.yml"
components:
    present:
        ontowiki:
            image: aksw/dld-present-ontowiki
            port: 8080